Passive elements in MRAM embedded integrated circuits

ABSTRACT

An integrated circuit device ( 300 ) comprises a substrate ( 301 ) and MRAM architecture ( 314 ) formed on the substrate ( 308 ). The MRAM architecture ( 314 ) includes a MRAM circuit ( 318 ) formed on the substrate ( 301 ); and a MRAM cell ( 316 ) coupled to and formed above the MRAM circuit ( 318 ). Additionally a passive device ( 320 ) is formed in conjunction with the MRAM cell ( 316 ). The passive device ( 320 ) can be one or more resistors and one or more capacitor. The concurrent fabrication of the MRAM architecture ( 314 ) and the passive device ( 320 ) facilitates an efficient and cost effective use of the physical space available over active circuit blocks of the substrate ( 404, 504 ), resulting in three-dimensional integration.

TECHNICAL FIELD

The present invention relates generally to electronic devices. Moreparticularly, the present invention relates to an integrated circuitdevice that includes Magnetoresistive Random Access Memory (MRAM)structures and passive device structures formed on a single substrate.

BACKGROUND

In contrast to Random Access Memory (RAM) technologies that useelectronic charges to store data, MRAM is a memory technology that usesmagnetic polarization to store data. One primary benefit of MRAM is thatit retains the stored data in the absence of applied system power, thus,it is a nonvolatile memory. Generally, MRAM includes a large number ofmagnetic cells formed on a semiconductor substrate, where each cellrepresents one data bit. Information is written to a bit cell bychanging the magnetization direction of a magnetic element within thecell, and a bit cell is read by measuring the resistance of the cell(e.g., low resistance typically represents a “0” bit and high resistancetypically represents a “1” bit).

A MRAM device generally includes an array of cells that are programmedusing programming lines, often called conductive bit lines andconductive digit lines. MRAM devices are fabricated using knownsemiconductor process technologies. For example, the bit and digit linesare formed from different metal layers that are separated by one or moreinsulating and/or additional metal layers. Conventional fabricationprocesses allow distinct MRAM devices to be easily fabricated on adevoted substrate.

The miniaturization of many modern applications make it desirable toshrink the physical size of electronic devices, integrate multiplecomponents or devices into a single chip, and/or improve circuit layoutefficiency. It is desirable to have a semiconductor-based device thatincludes a MRAM architecture integrated with passive elements, such asresistors and capacitors on a single substrate, where the MRAMarchitecture and the passive elements are fabricated using the sameprocess technology. Furthermore, other desirable features andcharacteristics of the present invention will become apparent from thesubsequent detailed description and the appended claims, taken inconjunction with the accompanying drawings and the foregoing technicalfield and background.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be derived byreferring to the detailed description and claims when considered inconjunction with the following figures, wherein like reference numbersrefer to similar elements throughout the figures:

FIG. 1 is a schematic perspective view of a simplified MRAM architecturein accordance with an exemplary embodiment of the invention;

FIG. 2 is a schematic perspective view of a MRAM cell configured inaccordance with an example embodiment of the invention;

FIG. 3 is a simplified cross sectional view of an integrated circuitdevice configured in accordance with an example embodiment of theinvention;

FIG. 4 is a cross sectional view of a resistor fabricated on the samesubstrate as a MRAM cell in accordance with an exemplary embodiment ofthe invention;

FIG. 5 is a cross sectional view of a resistor fabricated on the samesubstrate as a MRAM cell in accordance with another exemplary embodimentof the invention; and

FIG. 6 is a cross sectional view of a capacitor fabricated on the samesubstrate as a MRAM cell in accordance with another exemplary embodimentof the invention.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the invention or the application and uses ofthe invention. Furthermore, there is no intention to be bound by anyexpressed or implied theory presented in the preceding technical field,background, brief summary or the following detailed description.

For the sake of brevity, conventional techniques and features related toMRAM design, MRAM operation, semiconductor device fabrication, and otheraspects of the integrated circuit devices may not be described in detailherein. Furthermore, the circuit/component layouts and configurationsshown in the various figures contained herein are intended to representexemplary embodiments of the invention.

FIG. 1 is a schematic perspective view of a simplified core MRAM bitarchitecture 100 that is formed on a substrate (not shown) using asuitable semiconductor fabrication process. Although FIG. 1 illustratesa MRAM architecture 100 that includes only nine cells, a typical MRAMdevice will typically include a much larger number of cells (e.g.,millions of cells). Generally, MRAM architecture 100 includes at leastone electrode 104 formed from one metal layer, at least one electrode106 formed from another metal layer, and a Magnetic Tunnel Junction(“MTJ”) core 102 formed between the two metal layers. The MTJ core 102includes cells that form an array of memory locations for MRAMarchitecture 100.

FIG. 2 is a schematic perspective view of a MRAM cell 200 configured inaccordance with an exemplary embodiment of the invention. Some or allcells in MRAM architecture 100 may be configured as shown in FIG. 2.MRAM cell 200 includes an MTJ core 102 having a first ferromagneticlayer 202, a second ferromagnetic layer 204, an insulating layer 206interposed between the two ferromagnetic layers, and a bottom electrode207 that is coupled to the second ferromagnetic layer 204. In thisexample, first ferromagnetic layer 202 is a free magnetic layer becausethe direction of its magnetization can be switched to change the bitstatus of MRAM cell 200. Second ferromagnetic layer 204, however, is afixed magnetic layer because the direction of its magnetization isengineered not to rotate or change directions with normal write fields.When the magnetization in first ferromagnetic layer 202 is parallel tothe magnetization in second ferromagnetic layer 204, the resistanceacross MRAM cell 200 is lower than when the magnetization in firstferromagnetic layer 202 is anti-parallel to the magnetization in secondferromagnetic layer 204. The data (i.e., a “0” or “1”) in a given MRAMcell 200 is determined by measuring the resistance of the MRAM cell 200.The techniques utilized to read and write data to MRAM cell 200 areknown to those skilled in the art and, therefore, will not be describedin detail herein.

FIG. 2 also depicts a bit line 208, which can be formed in a layer knownas the Metal Global Interconnect (MGI) layer and a digit line 210, whichcan be formed in a layer known as the Metal Digital Line (MDL) layer,which will be individually and collectively referred to herein asprogram lines, corresponding to MRAM cell 200. The orientation of themagnetization in first ferromagnetic layer 202 rotates in response tocurrent magnitude and current direction flowing in digit line 210 and inresponse to current magnitude and direction flowing in bit line 208. Ina typical MRAM cell 200, the orientation of the bit is switched byreversing the polarity of the current in bit line 208 while keeping aconstant polarity of the current in digit line 210. In a toggle bit ofMRAM cell 200, the orientation of the bit is switched by a sequence ofcurrent pulses from the program lines bit line 208 and digit line 210).In an exemplary embodiment, bit line 208 may be connected to any numberof similar MRAM cells (e.g., a column of cells) to provide a commonwrite current to each of the connected cells. Similarly, digit line 210may be associated with any number of similar MRAM cells (e.g., a row ofcells) to provide a common digit current to each of the cells. Anexemplary matrix configuration is schematically illustrated in FIG. 1.

In the exemplary embodiment shown in FIG. 2, digit line 210 comprises aconductive digit element 212 and a permeable cladding material 214formed from a soft magnetic material. In this example, cladding 214partially surrounds conductive digit element 212. In particular,cladding 214 is formed around three sides of conductive digit element212 such that the inward facing surface of conductive digit element 212remains uncladded. In the preferred embodiment shown in FIG. 2, bit line208 includes a conductive bit element 216 and cladding 218 formed from amagnetic material. In this example, cladding 218 is formed around threesides of conductive bit element 216 such that the inward facing surfaceof conductive bit element 216 remains uncladded. Cladding 214/218 canfocus the magnetic flux toward the MTJ 102 to improve the efficiency inprogramming the MRAM cells 200. The cladding also reduces the writedisturbance to neighboring bits. In exemplary embodiments, the magneticcladding is an integral part of the barrier layers used in thefabrication of conductive program lines, such as copper, used in theMRAM process.

In one exemplary embodiment, conductive digit element 212 and conductivebit element 216 are formed from an electrically conductive material suchas copper, and cladding 214/218 is formed from a soft, permeableferromagnetic materials such as NiFe, a nickel-iron-cobalt alloy, acobalt-iron alloy, permalloy, or the like. In one example embodiment,cladding 214/218 is within the range of approximately 25 to 2000Angstroms thick and typically about 50 to 300 Angstroms thick. Thesidewalls of cladding 214/218 may be slightly thinner. Although theconductive elements and the cladding are realized from differentmaterials, conductive digit element 212 and cladding 214 are consideredto be fabricated at one common metal layer (e.g., the metal four layer),and conductive bit element 216 and cladding 218 are considered to befabricated at another common metal layer (e.g., the metal five layer).

A cross sectional view of an exemplary embodiment of the presentinvention is illustrated in FIG. 3. In FIG. 3 an integrated circuit 300includes a substrate 301, MRAM architecture 314, and smart powercomponents 306. Integrated circuit 300 can be manufactured using afabrication technology that includes a front end fabrication process anda back end fabrication process. Therefore, integrated circuit 300 caninclude elements or features that are formed using front end fabricationprocesses and elements and features that are formed using back endfabrication processes. During the front end fabrication process, variouselements or features are formed in front end layers 304 and during theback end fabrication process, various elements or features are formed inback end layers 302. These layers can include metal layers, conductivelayers, dielectric layers and other types of layers and can be formedusing any of a number of well known fabrication processes. Since frontend fabrication processes are completed prior in time to back endfabrication processes, front end layers 304 are located above thesubstrate 301 but below the back end layers 302.

The MRAM architecture 314 includes a MRAM circuit 318 that is formed inthe front end layers 304. The smart power component 306 comprises apower circuit 308; an Analog power control circuit 310 and a logiccontrol circuit 312 are formed on the substrate 301 and are manufacturedusing a front end fabrication process. In an embodiment of the presentinvention, the MRAM circuit 318 and the smart power component 306 can bemanufactured concurrently during the front end fabrication process. MRAMcircuit component 318 may include any number of elements or featuresthat support the operation of MRAM architecture 314, including, withoutlimitation: switching transistors; input/output circuitry; a decoder;comparators; sense amplifiers, or the like.

MRAM cell 316, which is also part of the MRAM architecture 314, andpassive components 320 are formed in back end layers 302 using back endfabrication processes. In one exemplary embodiment of the presentinvention, the materials used to manufacture MRAM cell 316 can also beuseful in the fabrication of passive components 320. Thus, passivecomponents 320 can be manufactured concurrently during the front endfabrication process.

MRAM architecture 314 may be generally configured as described above inconnection with FIGS. 1 and 2. Indeed, integrated circuit 300 may employconventional MRAM designs and techniques for MRAM architecture 314, andsuch conventional features will not be described in detail herein.Generally, as shown in FIG. 3, MRAM architecture 314 includes the MRAMcircuit component 318 formed in the front end layers 304 and a MRAM cell316 formed in the back end layers 302 coupled to MRAM circuit component318.

In one exemplary embodiment of the invention, power circuit component308 includes one or more high power MOSFET devices that are configuredto operate at high voltages to generate high currents. Alternateembodiments may employ different power generation devices and techniquesfor power circuit component 308. Digital logic component 312 may berealized with CMOS transistors or any suitable digital logicarrangement. Digital logic component 312 is configured to carry out thedigital operations that support the smart power architecture ofintegrated circuit 300. Analog power control circuit 310 includes analogcircuit components configured to support the smart power component ofintegrated circuit 300. Analog power control component 310 may include,for example, resistors, capacitors, inductors, MOSFETs, bipolar devices,and/or other analog circuit elements.

Passive components 320 are components that do not provide anyamplification or gain. In one embodiment of the present invention,passive components 320 can be resistors and capacitors. In the presentinvention, as discussed previously, the passive components 320 can beconstructed during the process steps used to fabricate the MRAM cell316. Thus, a passive component is formed in conjunction with a MRAM cell316 when at least part of the passive device is formed in the same layeras an element of MRAM cell 316. The passive components 320 can be usedwith the smart power components 306.

FIG. 4 is an exemplary embodiment of an integrated circuit 400 thatincludes a resistor integrated with a MRAM (not shown) and smart powercomponents (not shown). Many of the materials that are used in themanufacture of the MRAM cell also have good resistive qualities. Forexample, the bottom electrode of the MTJ core (referred to in thespecification as a metal MTJ layer or a MMTJ layer), can be used to forma resistor. The material used to manufacture the Metal LocalInterconnect (MLI) layer and the materials used to form the MTJ core canserve as resistors. Also, a series of resistors can be formed byconnecting resistive elements formed on one or more layers.

Integrated circuit 400 includes a substrate 404, front end layers 405formed over the substrate 404 and back end layers 406 formed over thefront end layers 405. The back end layers comprise first back end layers407 and second back end layers 408. A dashed line 409 represents adividing line between the first back end layers 407 and the second backend layers 408. The size of the front end layers 405, the back endlayers 406 and the dashed line 409 dividing the first back end layers407 and the second back end layers 408 are shown for exemplary purposesonly and the size can vary.

First back end layers 407 can include a metal one layer 412, a metal twolayer 414, and a metal three layer 416 connected by conductive vias 419.The first back end layers 407 may also include various dielectric layers(not shown). The smart power components 306 (not shown in FIG. 4) andthe MRAM circuit components 318 (not shown in FIG. 4) are formed in thefront end layer 405 and, in some exemplary embodiments, first back endlayers 407, using metal one layer 412, metal two layer 414 and metalthree layer 416, where appropriate.

Second back end layers 408, in this exemplary embodiment, can include ametal five layer 422, a MMTJ layer 426, a MLI layer 428 and conductivevias 430. The second back end layers 408 also include various dielectriclayers, which, for simplicity sake, are not illustrated in FIG. 4. Inthis exemplary embodiment, both a MRAM cell and a resistor can befabricated together.

In one exemplary embodiment of the present invention, a resistor 450 isformed in the second back end layers 408. In this exemplary embodimentthe resistor 450 includes a resistor element 452. In this exemplaryembodiment, resistor element 452 is formed in the MLI layer 428. TheMMTJ layer 426 and the MTJ layer (not shown) are used to provideelectrical connections and are not used as a resistor. An input 460 andan output 462 are formed at the metal four level 422. As noted before,the digit line 104 of the MRAM is also formed in the metal four level422. The input 460 and the output 462 are electrically coupled to thesubstrate for use by the power components.

In one exemplary embodiment, resistor element 452 is manufactured from athin layer of tantalum nitride (TaN). The resistor 450 is formed overthe logic circuitry, which improves the layout efficiency.

In another exemplary embodiment, materials in different layers of theback end layers act as resistors in series. FIG. 5 illustrates anintegrated circuit 500 having a substrate 504 upon which front endlayers 405 are formed. Back end layers 406 are formed over the front endlayers 405 and comprise first back end layers 407 and second back endlayers 408. Imaginary line 409 divides first back end layers 407 andsecond back end layers 408.

First back end layers 407 can include a metal one layer 510, a metal twolayer 512, and a metal three layer 514. The metal layers are connectedby conductive vias 516. First back end layers 407 may also includevarious dielectric layers (not shown). Smart power components 306 andMRAM circuit components 318 (both not shown) can be formed in the frontend layers 405 and, in some designs, in first back end layers 407 using,metal one layer 510, metal two layer 512, and metal three layer 514,when appropriate.

Second back end layers 408, in this exemplary embodiment, can include ametal four layer 520, a MMTJ layer 522, a MTJ layer 524 and a MLI layer526, connected by vias 528. The MTJ layer 524 is illustrated as a singlelayer in FIG. 5 but, as illustrated in FIGS. 1-2 and discussedpreviously, the MTJ layer 524 comprises a first ferromagnetic layer 202,a second ferromagnetic layer 204, and an insulating layer 206 betweenthe two ferromagnetic layers.

In one exemplary embodiment, a resistor 530 is comprised of severalindividual resistors elements connected in series. A first resistorelement 532, a second resistor element 534, and a third resistor element536 are formed in MMTJ layer 522. As discussed previously, MMTJ layer522 is the same layer where the bottom electrode of the MRAM can beformed. A fourth resistor element 538, a fifth resistor element 540, asixth resistor element 542, and a seventh resistor element 546 areformed in the MTJ layer 524, the same layer where the MTJ core 102 isfabricated. An eighth resistor element 548 and a ninth resistor element550 are formed in the MLI layer 526.

In the exemplary embodiment of FIG. 5, the resistor elements formed inthe MTJ layer 524 are formed from the same material as the MTJ core 102of the MRAM cell 200. Therefore, the resistors fabricated in the MTJlayer 524 can be set to one of the two resistive states depending on ifthe magnetization in the first ferromagnetic layer 202 is parallel oranti-parallel to the direction of the second ferromagnetic layer 204.Therefore, by switching the magnetization of the first ferromagneticlayer 202, the resistance of resistors formed in the MTJ layer 524 canbe adjusted between the two values. Thus, resistor elements in the MTJlayer 524 are adjustable.

In addition, the resistors in the MTJ core 102 can be disabled whenexcessive voltage is applied. The excessive voltage ruptures theinsulating layer 206, which results in the shorting of the resistorelement. Those skilled in the art can adapt the exemplary diagrams toallow the isolation of specific resistors thus creating an array offusable resistors. By using this method, a combination of resistorsforming an array can be configured to provide a range of resistorvalues.

In addition to providing resistors that are fabricated on the sameintegrated circuit as a MRAM device, capacitors can also be integratedwith MRAMs and smart power components. FIG. 6 illustrates a capacitor602 formed in conjunction with a MRAM device (not shown) and on the sameintegrated circuit 600. Capacitors store electric charge and typicallyconsist of a dielectric material or insulation interposed between twoconductors. In an exemplary circuit 600 of FIG. 6, the bottom electrode614 is formed at the MLI layer. In an exemplary embodiment, the bottomelectrode 614 is made from TaN. A dielectric layer is formed over thebottom electrode 614. In one embodiment, the dielectric layer comprisesa 1,000 angstrom layer of TEOS (tetraethylorthosilicate derived silicondioxide) 604 and a 650 angstrom layer of plasma enhanced nitride (PEN)604. A top electrode 612 is formed over the dielectric layer 604 at theMGI layer. In one exemplary embodiment, the top electrode 612 is madefrom copper. In the present invention, the bit line 106 of the MRAM canbe fabricated at the same layer as the top electrode 612. The bottomelectrode 614 can be electrically coupled to the MTJ layer 616 by afirst via 610. The top electrode 612 (MGI) is electrically coupled tothe metal four layer 618 by a second via 613.

In an alternative embodiment, capacitor 602 can be manufactured usingthe material of the MLI layer (formerly the bottom electrode 614) as thetop electrode and the material of the MTJ layer 616 as the bottomelectrode and a dielectric, such as TEOS, between the MTJ layer 616 andthe MLI layer 614 where via 610 is shown. In yet another embodiment,capacitor 602 can be manufactured using the material of the MTJ layer616 of as the top electrode, the material of metal four layer 618 as thebottom electrode and a dielectric, such as PEN and TEOS, in a dielectriclayer, where via 611 is typically formed. Additionally, any or all ofthe above capacitor combinations can be used together.

In the preceding discussion, the elements of the resistors andcapacitors were discussed as being formed in specific back end layers.However, the exact name of the back end layers used to fabricateelements of the resistors and capacitors is unimportant in the teachingsof the present invention. In the present invention, resistors andcapacitors are formed in conjunction with a MRAM cell as long as theMRAM cell and at least one element of the resistor or the capacitorshare at least one common layer.

In summary, circuits, devices, and methods configured in accordance withexample embodiments of the invention relate to an integrated circuitdevice comprises a substrate and MRAM architecture formed on thesubstrate. The MRAM architecture includes a MRAM circuit formed on thesubstrate; and a MRAM cell coupled to and formed above the MRAM circuit.Additionally a passive device is formed in conjunction with the MRAMcell. In one embodiment, the passive device is a resistor. In anotherembodiment the passive device is a capacitor. The resistor can be aresistor element formed in the MLI layer, the MMTJ layer, or the MTJlayer. Or the resistor elements can combine in any of severalpermutations. If the resistor element is fabricated in the MTJ layer,then the resistor element comprises a first ferromagnetic layer, asecond ferromagnetic layer, and an insulating layer between the twoferromagnetic layers. The resistance of the resistor element can be setat a high state when the magnetization in the first ferromagnetic layeris anti-parallel to the magnetization in the second ferromagnetic layerand set to a low state when the magnetization in first ferromagneticlayer is parallel to the magnetization in second ferromagnetic layer.Additionally, if the resistor element is formed in the MTJ layer, theresistor element can be shorted by applying excessive voltage to theresistor element of the MTJ layer.

In one exemplary embodiment, the capacitor comprises a top electrodeformed in a metal six level, a bottom electrode formed in a MLI leveland a dielectric layer formed between the top electrode and the bottomelectrode. Alternatively, the capacitor comprises a top electrode formedin an MLI level a bottom electrode formed in an MMTJ layer and adielectric layer formed between the top electrode and the bottomelectrode.

A method of forming an integrated circuit device method comprisesforming, on the front end layers of the device, at least one powercomponent; forming, on the front end layers of the device, a MRAMcircuit; forming, on the back end layers, a MRAM cell; and forming, onthe back end layers, a passive device having a feature foundconcurrently with a feature of the MRAM cell. The step of forming, onback end layers, a passive device further comprises forming a resistorcomprising at least one resistor element on a back end layer on which afeature of the MRAM cell is fabricated. Also, the step of forming, onback end layers, a passive device further comprises forming a capacitorcomprising a top electrode, a bottom electrode and a dielectric betweenthe top electrode and the bottom electrode formed on back end layers,wherein at least one of the backend layers where the capacitor is foundis associated with a feature of the MRAM cell. If the resistor is formedon a MTJ layer, the resistor element comprising a first ferromagneticlayer, a second ferromagnetic layer, and an insulating layer between thetwo ferromagnetic layers. The resistance of the resistor element can beset at a high state when the magnetization in the first ferromagneticlayer is anti-parallel to the magnetization in the second ferromagneticlayer and set to a low state when the magnetization in firstferromagnetic layer is parallel to the magnetization in secondferromagnetic layer. Additionally, if the resistor has a resistance, andthe resistor comprises a plurality of resistor elements, a portion ofthe plurality of resistor elements can comprise a resistor elementformed on a MTJ layer and a least one of the plurality of resistorelements are formed on the MTJ layer; wherein the resistor elementsformed on the MTJ layer can be shorted to change the resistance of theresistor.

An integrated circuit device comprises a substrate; a plurality of firstend layers formed over the substrate; a MRAM circuit formed in theplurality of first end layers; one or more power components formed inthe plurality of first end layers; and a plurality of back end layersformed over the front end layers. The back end layers include a magneticrandom access memory (“MRAM”) cell formed in the plurality of back endlayers. The MRAM cell is coupled to the MRAM control and comprises atleast one digit line, at least one bit line, and a magnetic tunneljunction core coupled between the at least one digit line and the atleast one bit line. Further, at least one passive device is formed inthe plurality of backend layers, wherein at least part of the passivedevice is fabricated when at least a portion of the MRAM cell isfabricated. The passive device can have one or more resistors and/orcapacitors.

The exemplary embodiment or embodiments described herein are notintended to limit the scope, applicability, or configuration of theinvention in any way. Rather, the foregoing detailed description willprovide those skilled in the art with a convenient road map forimplementing the described embodiment or embodiments. It should beunderstood that various changes can be made in the function andarrangement of elements without departing from the scope of theinvention as set forth in the appended claims and the legal equivalentsthereof.

1. A method of forming an integrated circuit device on a substrate, saidmethod comprising: forming front-end layers of the device on thesubstrate; forming, on the front-end layers of the device, at least onepower component; forming, on the front end layers of the device, a MRAMcircuit; forming back-end layers over at least a portion of thefront-end layers; forming, on the back end layers, a MRAM cell; andforming a plurality of resistor elements on back end layer on which afeature of the MRAM cell is fabricated, a portion of the plurality ofresistor elements comprising a resistor element formed on a MagneticTunnel Junction layer and wherein at least one of the portion of theplurality of resistor elements can be shorted to change the resistanceof the resistor.
 2. The method of claim 1 wherein the step of forming aplurality of resistor elements further comprises forming a capacitorcomprising a top electrode, a bottom electrode and a dielectric betweenthe top electrode and the bottom electrode formed on back end layers,wherein at least one of the backend layers where the capacitor is foundis associated with a feature of the MRAM cell.
 3. The method of claim 1wherein the step of forming a plurality of resistor elements includesforming at least a first resistor element comprising a firstferromagnetic layer, a second ferromagnetic layer, and an insulatinglayer between the two ferromagnetic layers, wherein the resistance ofthe first resistor element can be set at a high state when themagnetization in the first ferromagnetic layer is anti-parallel to themagnetization in the second ferromagnetic layer and set to a low statewhen the magnetization in the first ferromagnetic layer is parallel tothe magnetization in second ferromagnetic layer.